Machine-switching telephone-exchange system



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MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed May 2l, 1919 4 Sheets-Sheet 2 L. PQLIN KOM/SKY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed May 2l, 1919 MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed May 21, 1919 4 smug-snee@ i l 16H7@ ik 577W 59,5.:

Patented Ang., l2, i941a tot,

LIPA POLINKOWSKY, QF NEW YO'RK, `N. Y., ASSIGNOR T0 WESTERN ELECTRIC COIVI- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MACHINE-SWITCI-Ilbf TELEPHONE-EXCHANGE SYSTEM.

Application led May 21,

To @ZZ fr0/om 'it may concern.'

Be it known that I, LIPA PoLINKowsKY, a citizen of Russia, residing at New York, in the county of New York and State of New York, have invented certain new and useful Impr'oifements in h/iachine-Switching Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

rilhis invention relates to telephone eX- change systems in which machine switching apparatus is used for setting up connections between subscribers lines.

More particularly it has to do with a telephone syste-1n involving a plurality of eX- changes or switching stations provided with interconnecting trunk lines, whereby a subscribers line terminating in one switching station may be extended by automatic switches therein to an outgoing trunk, and thence over switches in the distant exchange or switching station into connection with a desired line.

An object of the invention is to provide, in a system of this character where interconnecting trunk circuits are arranged between switchingstations, means whereby the subscriber of a line local to one of such stations is enabled to transmit impulses by his sender over a two-conductor impulse transn'nitting` circuit, which is free 'from impedances, bridges, ground, or other connections, to a distant station to control the setting of selective switches therein.

A feature of the invention consists in arranging means such that after impulses have been sent trom one station over a trunk line to the distant station, and the switches therein have completed their operation in accordance with the designation sent, the impulse transmitting circuit is automatically conn verted into a 'talking circuit by connecting a source of talking current thereto at the iirst station.

A. further feature is the provision of a three-conductor trunk circuitbetween switching stations, two ofwhich conductors form a circuit for sending impulses directly from the subscribers line at the first station to a distant station, together with means such that after the switches in the distant station have been operated, a timed control is exercised Serial No. 298,707.

over the third conductor of the interhave been operated, a predetermined time opening ot the third conductor of the interconnecting trunk serves to connect in the talking battery at the first station, while the opening oi' the third conductor Jfor a longer interval brings about the release of the switches at the first switching station.

Such other features as are contemplated by the present invention will become apparent trom the following description and appended claims.

ln the drawings Fig. l shows a subscribers line leading to a satellite and the detailed circuits oi' a iirst line finder switch and a second line iinder switch for entending `the line 4to a trunk circuit which leads to a'. distant exchange.

There is also shown in this ligure the outgoing end of such a trunk circuit together with means controllable over the trunk Yfrom the distant exchange for connecting talking battery to the trunk` in the satellite, and ior causing the release ot the finder switches.

Fig. 2 shows the incoming end ci the trunk line at the. distant exchange and the circuits of a group selector switch for eX- tending the same to succeeding selector switches to complete the connection with the called. subscribers line.

Figs. 3 and 4C illustrate the circuit arrangement oit a register controlling equipment adapted to be set by impulses transmitted from from

the calling line over the trunk circuit the satellite to the exchange, for the purpose of controlling the Selective operation of the automatic switches.

reading the drawings, Figs. l and 2 should be taken in order from left to right with Fig. 3 below Fig. 2, and Fig. 4 to the lett of Fig. 3.

The switches employed in this system may 100 be of the same general construction and 0peration as the one shown in the patent to McBerty No. 1,097,868, granted May 26,

The controlling sequence switches and registers are of the same type and construction as the one described in detail in the patent to Reynolds and Baldwin 1,127,808, issued February 9, 1915.

It is believed that a more comprehensive understanding of the invention may be given by describing in detail the operation of the system in which the same is embodied in the establishment of a connection from one subscribers line to another. l

Assume first that the subscriber at the substation 600 belonging to a satellite or other switching station, desires to obtain a talking connection with a subscribers line, such as line 650 belonging to a distant exchange or switching station. On removing his receiver from the switchhook, a circuit is established from battery through the left-hand winding of the line relay 604, outer contact and armature of cut-oli relay 607, over the loop ot the calling line, inner armature and contact of relay 607, through the night-hand winding oi' rela-y 604 to ground. rlhe line relay 604, by attracting its armatures, closes a circuiti irc-m battery through the inner windings of the common starting relays 605, armature and contact of. rela-y 604 to the multiple terminals 614 of all iirst line linders having access to the group in which the calling line appears. T his causes a selectable potential to be placed upon these multiple terminals to identity the calling line. Upon the energization of the relay 605 a circuit is closed i'rom ground, over the tarmatures and contacts of these relays, and

'thence in parallel through the windings ot the magnets 606 of all idle first line finders, back contacts and armatures of relays 610, to battery and ground at the contacts and armature of relays 13 of such idle iinders. The power magnets 606 cause, in the wellknown manner, the rotation of the brush carriage oi" the line finder switches to search for the calling lineV It' the test brush of an idle lirst line3 tinder chances to be in contact with the terminal 614, or as soon as a nder advances its test brush into engagement with such terminal, the selectable condition is found thereon and a circuit is completed through the right-hand high resistance winding of test relay 609, to ground. The relay 609 receives suiiicient current to energize in this circuit, and by attracting its armature closes a. circuit through its lefthand low resistance winding, and the winding of the second test relay 610 to ground in shunt of lits high resistance winding. The resistance of this latter circuit being relatively low, the potential on test terminal 614 is suiiiciently reduced so that other line finder switches will not stop on the terminals of the calling line. The brush carriage continues to rotate until its brushes are accurately centered upon the terminals of the calling line, at which time the interrupter brush 615 is out of contact with its coopern ating segment, and the short circuit around relay 610 being thus removed, said relay energizes. The relay 610. by attracting its armature, opens the circuit ot power magnet 606 and closes a` circuit from battery, armature and contact of relay 613, armature and front contact of relay 610 through the winding ot holding magnet 611`I through the windings ot common starting relays 612. to ground. The holding magnet 611 brings the brush carriage to rest. A circuit is also completed from battery, armature and contact of relay 6137 armature and front contact of relay 610, `to the multiple terminals 630 in the second line finder switches, to place a selectable potential thereon.

The second line finder switches are ar ranged in pairs so that when both switrhes ot a `pair are idle only one is started in operation upon the initiation of a call. To accomplish this one second line {inder switch of each pair is provided with an additional relay 677 The test relay 674 of the other line finder of the pair may be wired so that the connection of its right-hand winding to ground leads over the left-hand armature and contact ot relay 677 by way of a lead. 619 which may be connected as shown al;

the cross 61.6. The leads 617 and 618 may` be connected. at the cross 699 in the power' circuit of the second line inder switch ot the pair, so that such power circuit is normally maintained open at the armature and contact ot relay 677. Vhen the linder switch of the pair provided with the relay 677 is busy this relay will be energized, as hereinafter shown` to close the circuit to ground of the right-hand winding oi test relay 674 ot the other finder switch ot the pair, and the right-hand armature of relay 677 closes ther break in the power circuit of said other inder switch. ln this manner the initiation of a second call during the time the first switch of each pair is busy causes the operation ot the second finder switch of each pair.

Vhen the Starting relays 612 energized, a circuit was closed from battery over the armatures and contacts of these 'relays in parallel through the power magnets 621 of one idle second line Iinder switch of each pair, and thence over the back contact and armature of relay 672, right-hand armature and contact of relay 676, to ground at the right-hand armature and back contact of relay 67 8. The brush carriages of the second line tinder switches are thereupon rotated to advance the test brushes over the multiple terminals in search of the connecting circuit leading from the calling first line finder. As soon as the second line linder moves its test brush into engagement with the multiple terminal 630 of this connecting circuit, the selectable condition is found thereon and an energizing circuit is com pleted through the rightdiand high resistance windingv of test relay 674 to ground, either directly or by way of lead 619 and the left-hand contact and armature oit relay 677 dependent upon which VFinder of the pair is taken for operation. The relay 674 operates and closes a low resistance path to ground through its lett-hand winding and the winding of relay 672, thus reducing the potential on the multiple terminals 630. As soon as the brushes are accurately centered, relay 672 energizes and opens the above traced circuit ot the power magnet 621, thus terminating the movement ofthe brush carriage. At the same time a circuit is closed from battery through the winding of relay 675, front contact and armature of relay 672, right-hand armature and contact of relay 676, to ground at the right-hand armature and back contact or relay 673. The relay 675 energizes and closes a circuit from battery through the winding of the cut-ott relay 607, relay 613, armature and back contact of relay 664, through the winding of relay 673, contact and armature of relay 675, to ground. Relays 607, 630 and 673 are energized whereas the meter magnet 603, which is connected in parallel with the circuit just traced, being marginal, does not operate at this time.

The relay 675 is constructed so as to attract its armature slowly.- Should two second line tindersstop at the same instant on the terminals of a calling circuit, and test relays 674 become operated, the parallel circuits established to ground through the low resistance relays 672 will not receive a suliicient flow oit current for both ot the relays 67 2 to remain energized. Consequently, the relay 672 of one of such linder switches will release its armature to open the circuit of relay 675 before this latter relay has had time to operate and close an energizing circuit for the relay 673, which in turn opens the circuit of the power magnet 621. This finder switch, therefore, continues to rotate without disturbing the calling circuit.

When the cut-od relay 607 energized it opened the circuit of the line relay 604 which released its armature and opened the circuit of the common starting relay 605. These relays, by deenergizing, interrupt the power circuits of magnets 606 to terminate the movement of all other rotating lirst line finders. The relay 613 by energizing and the test relay 610 byV deenergizing at this time open the circuit of the common relays 612, which in turn open the power circuit of all rotating second line finder switches, thus bringing the saine to rest.

Relay 673 which, as above noted, is energized in series with relays 607 and 613, closes a holding circuit for itself independent of the relay 675, traceable through the winding of relay 673, its lett-hand contact and armature, back contact and left-hand armature of relay 676 to ground at the iront contact and right-hand armature of 'relay 673. Relay 673 also closes a circuit for the relay 635 which leads trom ground over the right-hand armature and front contact of relay 673, armature and back contact of relay 678, through the windings of relays 635 and 677, to vbattery and ground. Relay 635 at its front contacts closes the normally opened talking conductors at the outgoing end of the trunk circuit which leads from the satellite to the distant exchange. The relay 677, as described, prepares circuits at the other line finder switch of the pair so that the same may now be taken :tor use in the event that another call is made while the nder switch shown is busy.

The relay 635 having closed the two conductors of the calling subscribers lines directly through to the distant exchange shown in Fig. 2, a circuit is established for the relay 622. This circuit leads from battery through the winding of said relay, contact 632 (1) of sequence switch 620, trunk conductor 655, right-hand armature and trout contact et relay 635, thence over the loop ot the subscribers line 600, and returning through the iront conta-ct and lett-hand armature oit' relay 635, trunk conductor 654, sequence switch contact 642 (l), home contact and interrupter brush 652, through the winding` of the relay 633, to ground. lVhen the relay 622 energizes, a circuit is closed from battery, through the winding ci" the sequence switch magnet 620, cont-act 647 (l), front contact and armature ot relay 622, to ground at the armature ot relay 631. Sequence switch 620 leaves position 1 and moves into position 4. As the sequence switch 620 reaches position 3, a circuit is closed from ground, over the armature and contact ot relay 663, sequence switch contact 636 to 13), left-hand armature and back contact of relay 624, third conductor 603 of the trunk circuit through the windings of relays 670 and 664, to battery and ground. Relay 670 energized but relay 664 being` ot the marginal type remains inert at this time. A circuit is thereupon closed in the satellite trom battery, armature and front contact of relay 670, through the winding of the slow-to-release relay 671 to ground, at the back contact and armature of relay 671. and also to ground, through the right-hand winding or slow-to-release relay 676. The relay 671 operates and completes a circuit at its armature and trout contact to hold the relay 673 energized before the circuit which is now holding ren lay 673 can be opened at the back contact and lett-hand armature oli' relay 676. which latter relay, it will be observed, attracts its' armatures as soon as the relay 671 removes the shunt from' around the righthand winding of such relay 676. As soon as the relay 676 operates, it closes a holdingcircuit over its left-hand winding, front contact and left-hand' armature to ground at the front contact and right-hand armature of rela-y 67 3. The circuits in the satellite remain in this condition until the switches at the exchange have completed their operation. y

As the sequence switch 620 reaches posi'- tion 3 andA also in position 4 thereof, battery current is connected' in bridge of the calli-ng line through the windings of relay 631 and retardation coil 623 by the closure of sequencel switch contacts 601 and 602.

In position 4 of sequence switch 620, the selection vof an idle registering mechanism takes place. For this purpose a testing s equence switch 680 isprovided to test the idle or busy condition of the register mechanisms, and upon finding an idle one, associates the same with the incoming end of the trunk line over which a callv has been extended. The circuit for initiating the testing operation of sequence switch 680 extends from battery, through the winding of the magnet of said sequence switch, contact 643 (4), back contact and armature of relay 638, which relay is now deenergized, contact 654 (4), contact 655 of sequence switch 680, closed in the consecutive positions l to 9, to ground. Vhen an idle register controlling mechanism is found, a circuit is completed from battery through the left-hand winding of relay 323, conta-ct 322 (l) of sequence 320 associated. with the register mechanism,A conductor 293, over a contact such as 655 closed in a position corresponding to the selected register mechanism, contact 639 (4), right-hand winding of relay 637 contact 655, closed in the consecutive half positions of sequence switch 630, to ground. The contacts such as. 65.6 of sequence switch 680 are arranged so that their circuit-closing positions extend over an angular distance sufficient to insure the closure ofthe above traced test circuit whenv contact 655 is in one of its successive half positions, this latter contact being arranged to make only brief closures. Relay 637 attracts its armature and closes a circuit through its left-hand low resistance winding, and the winding of relay 63S'to groundy in shunt ofthe right-hand winding of relay 637. The resistance of this circuit, be ing low, reduces the potential on the vconductor 293 such that the register controlling mechanism now tests'busy. Relay 633 at tracts its armature and opens the circuit just traced for the testing sequence switch 680, so that thisV sequence switch, upon arriving in its full position, comes to rest. A circuit is also established by relay 638 for sequence switch 620, which may be traced from' battery, through the winding` of such sequence switch contact 645 (4), front contact and armature of relay 638, contact 654 (4') to ground at sequence switch contact 655. Sequence switch 620 moves out of position 4- and into position 5. As the sequence switch 620 'passes out of position 4, the bridge across the calling` line through the rela-y 631 and retardation coil 623 is opened at contacts 601 and 602, and in position 5 the calling line is connected over these contacts to the stepping relay 325 of the register set. The circuit of relay may be followed from battery, through the lefthand winding thereof, left-hand contact of relay 301, contact 657 of sequence switch 680, contact 602 (5), trunk conductor 655, thence over the loop of the calling line and returning by way of trunlr conductor 654` sequence switch contacts 601 (5), contact 658, right-hand contact of relay 301 through the right-hand winding of relay 325 to ground.

It will be observed that the impulse circuit above traced, extending from the calling subscribers line through the satellite to the register mechanism at the exchange, comprises a two-conductor metallic circuit. that is free from impedances, bridges, hattery and ground connect-ions at the satellite, and that no repeating` devices are necessary to transfer the impulses sent out at the calling substation from the satellite to the eN- change.

At the time the register mechanism shown was selected by sequence switch 630, it will' be remembered the relay 323 was energized in series with the relay 637. Relay 32.", closes a circuit from battery. through the winding of sequence switch 320 through the right-hand winding of relay 3 3, front contact and armature to ground. Sequence switch 320 thereupon advances into posi^ tion 3. On leaving position 2, the original circuit through t-hc left-hand winding ol relay 323 is opened at contact 322 so that this relay deenergizes to' open the starting circuit of the sequence switch 320 bel'ore it can reach position 3. As relay 323 releases its armature and with sequence switch 320 in position 3, a circuit is closed from battery, contact 327 (3) through the winding of relay 326, back contact and armature ot relay 323 to ground, causing the energization of rela-y 326. The apparatus is now in condition foi` the calling subscriber to send impulses in accordance with the called line designation to position the register mecha` nism to subsequently control the selective operation of the automatic switches.

llVhile the drawings only show a first group selector at the exchange, it is to be understood that there are to be succeeding selector switches as, for example, a. final switch in which case three selecting operations are necessary to complete connection to the called line, The register controlling' equipment shown has a capacity suiicient to effect live controlling operations, there being :tive register sequence switches. lit desirable the exchange may be ot such a size as to necessitate a sufficient number oit selector switches to use all of 'the controlling registers, or, it desirable, a part or all ot the registers may be used to control selective switches in a distant exchange in case ot an outgoing call. For the purpose of the present description, it will be assumed that the exchange shown in this system only equipped with a. group selector and a iinal selector, whereby only three selective operations are necessary. ln this case the supscriber may dial a. series oi impulses to set each ot the controlling re; JVers, but since the call is one local to a` first exchange the last three registers alone are eii'ective to control the operation ot the selective switches therein. The type ot' registers used in this system is one in which the sequence switches are provided with ten positions. Each sequence switch advances to a position corresponding to the number ot impulses sent from the subscribers dial during the positioning period ont the registers, and later runs through the remaining` positions to its home position `to control the` operation ot the selective switches. lt is, therefore, ob- `rions that the number ci' steps t; u. by the register while controlling` a selec ve switch is the complement ot the number ot impulses sent by the calling subscriber. ln hrder that the switches be controlled in accordance with the numerical designations ot the called line, it only becomes necessary to arrange the subscribers sender so that the complement rather than the actual digit itself is sent to the controlling registers. rl`he subscribers dial is further arranged so that the last interruption oit the line ot' each inipulse'series is of a longer duration than the others. The reason tor this teature will appear hereinafter.

The stepping' relay 325 being` energized .in series with the calling` line over the circuit described closes a circuit from ground, over its armature and front contact, armature and front contact of relay 326, contact 330 (3), through the right-hand winding of differential relay 329, armature and baclr` contact of this relay, contact 328 through the winding,` ot the register 100, to battery and ground. Aparallel circuit for the left-hand winding of relay 329 is also closed to ground at the armature and contact ot relay 325. Both windings being` energized the relay 329 does not attract its armature. The register 100, however', energizes and moves out of position O. As the local Contact 101 01"' this register closes in the well known manner in the halt position between position O and position 1 directly to ground, the right-hand windingoit ditterential relay 329 is thereby shunted and said relay attracts its armature. yThe relay 337 is connected in. parallel to the register 1GO iu a circuit through the right-hand winding` of differential relay 329 and insures that the register moves 'fully out of each of its positions before the energizing' circuit ot such register can be opened by the relay 329. The register 100 under the control oit' its local contact 101 advances into its irst positionwhere it remains. As sequence switch 320 passed out ot position 1, the interrupter 333 was connected over sequence contact 332 to the winding' of a dialing` tone apparatus 324i. The calling' subscriber hearing; a distinctive tone in his receiver knows that he may proceed with the transmission ot impulses. Upony the lirst interruption ot the calling` line at the subscribers dial, relay 325 retracts its armature and opens the circuit ot the left-hand winding oft relay 329, which consequently becomes deenergized. As the line circuit again closes. the register 100 is energized once more and moves out ot position 1. Relay 329 again energizes,

the register passes to position 2 and at thel next interruption oit the line circuit, relay 329 becomes deenergized. This procedure continues the register advancing` one position upon each interruption of the line until the Afirst series ot impulses have been coinpleted. At each retraction of the armature at relay 325, a momentary circuit is com-r pleted overfcontact 331 (3) for relay 334. This relay, however, beingslow to energize does not attract its armature. At the last interruption of the line circuit which., as above noted, is comparatively longer than the proceeding interruptions of the series, the circuit ot relay 334-. is closed su'liiciently long to permit it to energize. ri. circuit. is now completed from battery, through the left-hand winding of relay 323 to ground at the contact and armature of relay 3341:. Relay 323 in turn closes a circuit to drive sequence switch 320 out of position 3. Before sequence switch 320 can have reached. position 5, the line circuit is again closed and relay 334 deenergized to in turn cause the deenergization ot relay 323, Sequence switch 320, therefore, comes to rest in position 5. Relay 326 which had its circuit opened at the back contact of relay 323 deenergized while sequence switch 320 was Lsassing from position 3 to position 5. ln passing through position 41. a circuit is closed over Contact 323 (t), 'contact and righthand armature and right-hand winding of relay 329, and contact 330 (4e) to advance the register 100 one step in addition to the position to which it was set by the subscribers sender.

llO

350, left-hand armature and contact ot relay 332, contact 339, closed in positions 2 to 4r, to ground at the right-hand armature ot relay 362. Relay 357 is energized to hold the fundamental circuit open while sequence switch is passing through positions 2 to e over a circuit from battery, through the winding` ot this relay, contact 330 to ground at. the right-hand armature oi relay 332.

As sequence switch 350 reaches position 2, a circuit is closed troni` battery through the right-hand winding ot ditlierential relay 359, contact and armature or relay 355, sequence switch contact 354, to ground. at contact 331. rl`he relay 359 energizes in this circuit.

Upon reaching position 5 the 'fundamental circuit tor controlling the selective O-peration ot the group selector shown in Fig. 2 is established This circuit may be traced from battery, through the winding oi relay 622, contact 630 (5) ot sequence switch 620, conductor 296, armature and 'i' contact of relay 357, through the winding` ot the stepping relay Contact 38() (5) of sequence switch 350, to ground at the right-hand armature of relay 332. Stepping relay 355, energizing, opens the circuit just traced 'ior relay 359 to permit the saine to deenergize. The relay 622 energizes in the fundamental circuit and closes a circuit from ground, armature and back contact oit relay 631, armature and front contact of relay 622, contact 645 (5) through the winding of sequence switch 620 to battery and ground. Sequence switch 620 Inoyes out of position 5 and into position 6. A circuit is now completed 'from battery through the winding of trip spindle magnet 643, contact 649 (6), iront contact and arn'iature ot relay 622, back contact and armature of relay 631 to groundu rllhe inagnet 64:3 energizes and the trip spindle rotates, closing in the well-knownv manner a set of interrupter contacts 659 as the trip spindle approaches each successire brush tripping position.

The stepping relay 355 also energizes in the fundamental circuit in series with relay `When the tripping spindle approaches the iii-st brush tripping position, the interruptor contact 659 closes a circuit directly to ground for relay 622 over sequence switch contact 632 (6). The stepping relay 355 is shunted by this path to ground, and releasingl its armature closes a circuit troni ground, contact 331, contact e (5), armature and contact ot the stepping relay 355 through the lett-hand winding ot differential relay 359, armature and contact ot this relay, contact 366 (5), contact 122 ot register 120, through the winding ot such register to battery and ground. A parallel circuit is also p closed for the right-hand winding of the ditterential relay 359 to ground at the contact 381.. Both windings ot relay 359 being simultaneously energized, it does not attract its armature. The register 120, however, which controls the operation of the group selector shown in Fig. 2, energizes and nieves out of the position to which it was set by the calling subscribers dial. Midway between positions the local Contact 121 ot' register 120, being connected directly to ground, short circuits the lett-hand winding of differential relay 359 which thereupon operates. The register under the control o'f its local contact advances to the next position. As the tripping spindle reaches its first position, the interruptor contact 659 is opened, relay 355 is again energized, and opening the circuit oit the right-hand winding oi' relay 359, perinits the latter to release its armature. On approach ot the tripping spindle to its next position, the interruptor 659 is closed and the stepping relay 355 deenergizes. The register y120 is energized as before in series with the lett-hand winding ot relay 359, and begins to nioyc to its next posit-ion. lVhen the local contact 121 closes, relay 359 energizes as described, opening the starting circuit ot the register 120, and the register now advances into position under control of its local contact 121. llilhen the tripping spindle has reached its second position the stepping relay 355 again cnergizes and the differential relay 359 in turn deenergizes. This operation continues, the register 120 advancing one position tor each deenergization of the stepping relay until it reaches its hoine position O. At the next deenergization ofi relay 355, after register 120 has arrived in position O, a circuit is coinpleted for relay 357 frein battery, to the winding oi' this relay, sequence switch contact 36-1 (5), contact 124- (O) ot register 120, contact 366 (5), contact and armature and lefthand winding ot relay 359, contact and armature ot relay 355, sequence switch con-- tact 354 (5), to ground at contact 331. A parallel circuit is also completed troni battery, through the winding of sequence switch 350, lett-hand armature and contact ot relay 332, contact 354 (5), Contact 121i- (O), contact 366 (5), contact and arn'iaturc and lett-hand winding o'l' relay 359, contactr and armature ot relay 355, contact 351i (5), to ground at contact 331. The sequence switch 350 moves out of position 5 and into position 6. Relay 357, energizing, opens the `'fundaincntal circuit to prevent any 'further operation of the register 120. As soon as the interruptor contact 659 opens, the 'fundamental circuit being broken at the register set, relay 622 deenergizes and closes a circuit troni battery, through the winding of sequence switch 620, contact 6416 (6), back contcat and arniature oill relay 622, to `ground at the baclr contact vand armature ot relay 631. Sequence the brush carriage to come to rest.

switch 620 moves from position 6 into position 7. In position 7 of sequence switch 620 the relay 622 is energized in a circuit 'from battery, through the winding of this relay, winding of relay 653, sequence switch contact 639, contact 656, conductor 293, back contact and armature of relay 339, contact 340 (4, to 15) of sequence switch 320, to ground. Relay 653 also energizes in this circuit. A circuit is now established 'for the brush carriage power magnet 644 of the group selector. This circuit is traceable trom battery, through the winding of such power magnet, contact 641 (7 back contact and armature of relay 638, trent contact and armature ot' relay 622, back contact and armature of relay 631, to ground.

The brush carriage of the group selector is rotated in the well-known manner, the set of brushes selected b y the tripping spindle are tripped and moves over the terminals such as terminals 690, 691 and 692 ot the level of trunks leading to the proper group tot final select-or switches. Then the test brush oit the group selector is advanced into engagement with the test terminal 692 of an idle trunk circuit, a selectable potential is found thereon and test relay 637 energizes in a circuit over contact 640 (7) through the righthand high resistance winding ot relay 637, back contact and armature ot relay 624, contact 654 (7 contact 655, to ground. The relay 637 energizes and closes a low resistance circuit through itsle'ft-hand winding and the winding of relay 638 to ground, thus reducing the potential on terminal 692 in the well-known manner. Then the brushes of the group selector are accurately centered on terminals 6,90, G91, 692, the interrupter brush 652 removes the short-circuit from around relay 638 and this relay, by energizing, opens the above traced power circuit ior the magnet 644, thus causing Furthermore, the energize-tion ot relay 638 closes a circuit from battery, through the winding` of sequence switch 620, contact 645 (7 to 8), front contact and armature of relay 638, front contact and armature ot relay 622, back contact and armature of relay 63]., to ground. Sequence switch 620 moves through position 8 and into position 9. ln position 9 of sequence switch 620, the fundamental circuit, comprising the two conductors 296 and 297, is extended over sequence switch contacts 630 and 651 to the selected `final switch.

When relay 653 energizes in series with relay 622, as sequence switch 620 reaches position 7 it closes a circuit to ground in shunt of the contact and armature of relay 663 to hold the relay 670 in the satellite energized. At the right-hand armature of relay 653, a circuit is completed for the energization of the slow-to-release relay 663.

The function of these two relays will be described hereinafter.

If at the time the group selector conipletes its limiting operation and seizes a trunk leading to a linal selector, the tens and units registers 130 and 140 have been positioned under the control of the stepping circuit from the calling subscribers line, the sequence switch 320, a-s above described, will have moved into position 14. The sequence switch 350, which moved into position 6 at the termination of the group selector brush tripping operation, awaits the movement ot sequence switch 320 into position 14, provided the latter has not already advanced to such position. A circuit is thereupon completed from battery, through the winding of sequence switch 350, contact- 352 (6), Contact 341 (14) of sequence switch 320, to ground. Sequence switch 350 leaves position 6 and goes into position 7 in which the fundamental circuit is closed at the register controlling mechanism. The 'fundamental circuit includes, as is well understood, the line relay ot the final selector switch (not shown) and extends over terminal 690, contact G51 (9), conductor 297, right-hand armature and contact of relay 383, contact 385 (7), through the winding of the stepping relay 355, contact and armature ot relay 357, conductor 296, sequence switch contact 630 (9), terminal 691 and thence to the final selector switch.

During the rotation ot the tripping spindle of the linal selector switch, the stepping relay 355 is short circuited in t-he usual manner, and each time it deenergizes, acircuit is completed from ground, contact 381, contact 354 (7), armature and contact of relay 355, through the left-hand winding ot relay 359, armature and contact. of this relay, contact 366 (7), contact 132 of the tens register 130, through the winding ot register 130, to battery and ground. In the manner above described in connection with the restoration of the register 120, the register 130 passes through one position tor each brush tripping position passed over by the tripping spindle ot the final selector switch. then register 130 reaches position O, a circuit is established from battery, through the winding of relay 357, contact 364, (7), contact 134 (O), contact 366 (7), contact and armature and left-hand winding ot relay 359, contact and armature of relay 355, contact 354 (7), to ground at contact 381. A parallel circuit is closed at the same time from battery, through the winding ot sequence switch 350, lett-hand armature and contact of relay 382, contact 364 (7), contact 134 (0), contact 366 (7) to ground as above traced at the contact 381. Relay 357 energizes to open the fundamental circuit while sequence switch 350 advances from position 7 into position 9.

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The fundamental circuit remains closed at the register controlling mechanism with sequence switch 350 in position 9 and when, at the final selector, the brush carriage is rotated in the well-known manner to perform the units selection the usual shunting o-f the stepping relay 355, as the brushes pass over the terminals of each line in the selected level, causes said relay to intermittently release its armature. At each deenergization of relay 355, a circuit is closed from ground, contact 381, contact 354 (9), armature and contact of relay 355, left-hand winding and armature and contact of differential relay 359, contact 367 (9), contact 142 of the units register 140 through the winding of this register to battery and ground. 1n the manner now already well understood the register 140 moves through one step for each operation of the stepping relay 355 until it reaches position 0. At this time the circuit is closed from battery, through the winding of relay 357, contact 364 (9), contact 144 (0), back contact and armature of relay 374, contact 145 to 0, contact 367 (9), contact and armature and left-hand winding of relay 359., Contact and armature of relay 355, contact 354 (9), to ground at contact 381. A circuit is also closed at this time from battery, through the winding of sequence switch 350, leftfhand armature and contact of relay 382 and thence to ground at the contact 381 in parallel to the circuit just traced for relay 357. The relay 357 opens the fundamental circuit, whereas sequence switch 350 moves from positio-n 9 into position 12.

ln passing through position 10 sequence switch 350 closes a circuit from battery, through the winding of relay 339, contact 368, contact and left-hand armature of relay 383, to ground at contact 369. The relay 339 by attracting its armature opens the circuit hereinbefore traced, which is holding relays 622 and 653 energized. Relay 622 deenergizes and closes a circuit from battery, through the winding of sequence switch 620, contact 646 (9), back contact and armature of relay 622, back contact and armature of relay 631 to ground, whereupon sequence switch 620 moves out of position 9. In position 10 the movement of sequence switch 620 is continued by means of a circuit closed over sequence switch contact 628 and the back contact and armature of relay 627, to ground. Sequence switch 620, therefore, comes to rest in position 11. y

)When sequence switch contacts 601 and 602 leave position 9, the circuit of the stepping relay 325 is opened, and deenergizing, this relay closes a circuit from ground, over its armature and back contact, contact 348 (14). through the winding of sequence switch 320, to battery, to drive said sequence switch out of position 14 and into posit-ion 15. 1n position 15 of sequence switch 3.20

normal position. The circuit for driving the register back Vto position 0 may be traced from battery, through the winding of such register contact 102, contact 361 (13) and contact 343 (15), to ground. On reaching position 0, register 100 completes a circuit from battery, through the winding of ,p

con- 3 sequence switch 350, contact 379 (13) tact 363 (13), contact 104 (0), contact 361 (13) and contact 341 (15) to ground to drive sequence switch 350 into position 14. rl`he second register is now driven back to its normal position to 0 in circuit from battery, through the winding of this register, contact 112, contact 361 (14), to ground at contact 343 (15). Vhen register 110 reachesposi P tion O, a circuit is completed from battery, through the winding of sequence switch 350, contact 379 (14), contact 363 (14), contact 114 (0), contact 361 (14), to ground at contact 343, whereupon sequence switch 350 moves out of position 14. In position 15 sequence switch 350 continues to move by means of a circuit closed from battery, through `the winding thereof, contact 379 (15), contact 364 (15), contact 124 of register now in position 0, contact 366 (15), to ground at contact 343. In position 16, sequence switch 350 continues to advance by means of a circuit from battery, through the winding thereof, contact 379 (16), contact 364 (16), contact 134 of register 130 now in position 0, contact 366 (16) and contact 343 to ground. In position 17 a circuit is completed to drive sequence switch 350 into its normal or first position from battery, .l

through the winding of said sequence switch contact 379 (17), contact 364 (17), contact 144 of register 140 now in position 0,'bacl` contact and armature of relay 374, contact 145, contact 367 (17) to ground at contact 343. Sequence switch 350 in its normal position, closes a circuit for relay 323 traceable from battery, through the left-hand winding of said relay, sequence switch contact 322 (15) and sequence switch contact 369 (1), to ground. Relay 323 attracting its armature closes a circuit over its right-hand winding to drive sequence switch 320 out of position 15. In position 17 of sequence switch 320 a circuit is closed for relay 334 over contact 331 (17), back contact and armature of relay 326, to ground at sequence switch contact 340 (17). Relay 334 energizes and closes a circuit for the left-hand winding of relay 323 and thereby maintains the energization of this latter relayso that sequence switch 320 passes over position 17 and comes to rest in its normal or lirst position. The register controlling. mechanism is now completely restored to its normal position and is ready to be. seized for controlling` other selective operations.

` Returning now to the point where relay 653 was deenergized at the time relay 339 of the controlling mechanism was energized, a description will be given ot the operationsproduced at the outgoing end ot the trunk circuit in the satellite by the operation of relay 653. On releasing its lett-hand armature relay 653 opens the circuit formerly traced for maintaining the energization of relay 670 in the satellite. Relay 663, which is energized at this time over a circuit including the right-hand armature of relay 653 maintains its armature attracted for a definite interval of time atter the release of relay 653 by reason of its slow-torelease character. Therefore, for the period of time that relay 663 requires to release its armature, the circuit of relay 670 is held open. Relay 670 on releasing its armature opens the circuit of relay 67 1 which controls the energizing circuits or' both relays 676 and 673.v The relay 671 is so constructed that it will not release its armature until after the expiration of a period great-er than that required for relay 663 to deener` gize. Relays 676 and 673 are consequently held energized during the time relay 663 is releasing its: armature. llhen relay 670 deenergizes it closes a circuit from battery,

over its armature and back contact through the left-hand Winding of relay 678, :trout contact and left-hand armature of relay 676, to ground at the front contact and right-hand armature otrelay 673. Relay 678 by attracting its armature, closes a locking circuit for itself in series with relay 679, traceable from battery, through the winding of relay 677, winding of relay 679, righthand winding, front contact and armature of relay 678, front contact and right-hand armature. of relay 673, to ground. Relay Y679 completes a circuit from battery,

through the winding of relay 668, righthand armature and contact otrelay 679, over the loop of the calling line and thence to ground by way ot the left-handarmature and contact ot relay 679 ,and the winding oit retardation coil 694. rlhe supply ot talking battery for the calling subscribers line is thus connected across the trunk circuit in the satellite. The relay 678 on attracting its armature opens the circuit hereinhefore traced .tor relay 635 which releases its armatures and closes the talking conductors a andr65r5 of the outgoing end ot the trunk circuit through the coil 660. Relay 631 is now .energized in a circuit to ground `through the retardation coil 623 in series with Vcoil 660. As soon as the slow-to-release relay 663 retracts its armature the original energizing circuit ot relay 67() is again closed and this relay operates to complete the temporarily opened circuit ot ielay 671, whereby relays 671, 676 and 673 are maintained energized.

The iinal selector having been more? iii the well-known manner undel the control o'tl the register mechanism to the terminals of the called line, such as linev 650, the usual test is made, ringing current applied and the changeover operations in the circuits olf the inal selector switch eil'ected. W hen the called subscriber answers relay 627 at the group selector is energized in series with the called line in a circuit extending to ground, through retardation coil 626 and the 'liront contact and armature of relay 631. Relay 627 energizing closes a circuit from ground over its armature and trout contact, sequence switch contact 6ft-5 (11), through the winding of sequence switch 620 to battery, whereupon sequence switch 620 moves into position 12 which is the talking` position thereof. The calling and called subscribers may now proceed with the conversation.

it the end ot the conversation when the calling subscriber replaces his receiver to the switchhook, relay 631 deenergizes and closes a circuit 'from ground, over its armature and back contact, armature and back contact ot relay 622, sequence switch contact 646 (12), through the winding of sequenee switch 620 to battery, to drive said sequence switch out of position 12 and through position 13 into position 1 7. In this position the brush carriage or the group selector is restored to normal position by means ot' a circuit from battery, through the winding of the power magnet 644, contact 641 (17), bac-k contact and armature oit relay 638, contact 654- (17), to ground at the contact 655. When the brush carriage reaches its normal position relay 638 is energized in a circuit 'from ground, through the winding thereof, interrupter 652 and its home contact, sequence switch contact 64:2 (17), to battery and ground. Relay 63S energizes and opens the circuit ot the power magnet 644e causing the brush carriage to cease rotating, and also closes a circuit from battery, through the winding oit sequence switch 620, cont-act 645 (17), front contact and armature oi relay 638, contact 6511- (17) to ground at contact The sequence switch 620 thereupon moves into position 18 where a circuit is closed trom battery, through the winding o' relay 627 and sequence switch Contact 629v` to ground. Re lay 627 energizcs and closes a circuit troni ground. over the armature and trout con* tact thereof, sequence switch contact 615 (18), through the winding ot sequence llS switch 620 to battery, to drive said sequence Switch out of position 18 and into its normal position 1. 'lhe group selector is now completely restored tol its normal position. The restoration of the final and other suc ceeding selector switches will take place in any wellknown manner.

When sequence switch 620 leaves position 13 during the release oit the connection, the original circuit of the relays 664 and 670 is opened at sequence switch contact 636, and anew circuit is immediately closed over said contact including a source ot current 659 and the armature and back contact of relay 624. The battery 659 is ot' such polarity that the current flowing in the circuit of relay 664 is now sutiicient to energize the same. Relay 664 attracts its armature and connects a source oltA metering battery in series with the meter magnet 603 which operates to charge the call. The circuit of relay 673, being opened at the back contact ot relay 664, this relay deenergizes whereupon the relays 677, 679 and 678 are permitted to release their armatures. When sequence switch 620 subsequently passes out or" position 16, sequence switch contact 636 is opened and relays 664 and 670 are released. The circuits ot' relays 671 and 676 are now opened, and these relays deenergize.' The cut-oli relay 607 also deenergizes at tlietime the circuit of relay 67 3 is opened at the back contact of the relay 664. rlhe apparatus in the satellite is now restored to its normal position ready to be taken for subsequent calls.

lf the called line is found to be busy or it the called subscriber does not answer, re lay 627 does not energize and consequently the sequence switch 620 stops in position 11. W'hen the calling subscriber hangs up his receiver and relay 668 deenergizes, thus causing the release of relay 631, a oir-uit is closed from ground, over the armature and back contact ot relay 631, armature and back contact of relay 622, contact 646 (11),

through the left-hand winding o1' relay 624,. to battery and ground. rRelay 624 operates and closes a circuit from battery, through the winding o sequence switch 620, right-.

hand winding, liront contact and armature ci rela 624, contact 654 (11), to Ground at the contact 655. Sequence switch 620 moves over positions 12 and 13 and comes to rest in position 17. ln this instance since the relay 624 is energized, the battery 659 is not applied to conductor 603 to operate the mar- ,i nal relay 664 as sequence switch contact moves over positions 14 to 16, and as a result the meter 608 is not operated to charge the call. `When sequence switch contact 636 leaves position 13, relay 670 is deenergized and after a sufficient interval of time the slow relay 671 releases its armature and restores to normal the circuits of the linder switches in the satellite.

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In position 17 of sequence switch 620, the restoration of the group selector takes place in the manner above described.

What is claimed is: 1. ln a telephone exchange system, a subscribers line, va switching station, a trunk line outgoing therefrom, a distant switching station in which said trunk terminates, switches at. said lirst station for connecting the subscribers line to said trunk, switches at said distant station for extending said trunk line, an impulse circuit including the talking conductors of said trunk which is free from impedances at the irst station for transmitting impulses from the subscribers line to the distant station to control the switches therein, a source of talking current associated with the talking conductors of said trunk circuit at the lirst station, and means for rendering said source of current effective for conversation.

2. In a telephone exchange system, a subscribers line, a switching station, a trunk line outgoing therefrom, a distant switching station in which said trunk terminates, switches at said irst station for connecting the subscribers line to said trunk, switches at said distant station for extending said trunk line, an impulse circuit including the talking conductors of said trunk which is lree from impedances, bridges, ground and other connections at the irst station for transmittino impulses from the subscribers line to said distant station to control the switches therein, a source of talking current connected to the trunk line at said first station, and means for rendering said source ot current eiective for conversation.

3. ln a telephone exchange system, a subscribers line, a switching-station, a distant switching station, a trunk circuit outgoing` from said lirst station to the distant station, switches at the lirst station 'for connecting the subseribers line to said trunk circuit, switches at the distant station for extending said trunk circuit, condensers and a source of talking battery connected in the trunk circuit at the tirstvstation, means for establishing an impulse circuit which is tree from impedances, bridges, ground and other connections at the first station and which includes the talking conductors of said trunk circuit for transmitting impulses from the subscribers line to the distant station to control the switches therein, said condensers and talking battery being inoperative during` the transmission of impulses, and means for disabling said impulse circuit and for rendering said condensers and talking battery effective for conversation.

4. ln a telephone system, a subscribers line, a switching station, a trunk line outgoing therefrom, a distant switching station in which said trunk terminates, switches at said first station for connecting the subscribers lll) line to said trunk, switches at said distant station for extending said trunk line, means for transmitting impulses from the suhscriloers line over said trunk line to the distant station to, control the switches therein, a source of talking current at said first station connected to said trunk line, means for opening one of the conductors of said trunk line for a predetermined time interval, and means responsive to such opening for rendering said source of current effective for conversation.

5. In a telephone system, `a subscrihers line, a switching station, atrunk line outgoing therefrom, a distant switching station in which said trunk terminates, switches at said first station for connecting the subscribers line to said trunk, switches at said distant station for extending said trunk line, a controlling mechanism for controlling the operation of the switches in said distant station, means for transmitting impulses from the suhscrihers line over said trunk line to the distant station to set said controlling mechanism, a source of talking current at said first station -associated with said trunk line, means operated by said controlling` mechanism at the completion oit its operation for opening one of the conductors of said trunk line for a predetermined interval of time, and means responsive to such opening for rendering said source of current effective for conversation.

6. In a telephone system, a subscribers line, a satellite, a trunk line outgoing thererom,'an exchange to which said trunk line leads, switches at said satellite for connecting the suloscriloers line to said trunk, switches at the exchangecfor extending said trunk, a set of registers for controlling the' operation voi the switches in the exchange, means for transmitting impulses from the subscribers line over said trunk line to the exchange to set said registers, a source of talking current in the satellite associated with said trunk line, means operated by said registers upon the completion of their controlling operation for opening one of the conductors of said trunk line for a predetermined yinterval of time, and means responsive to such opening for rendering said source of current eliective for conversation.

7. In a telephone system, a suhscrihers line, a switching station, a three-conductor trunk line outgoing therefrom, a distant switching station to which ksaid trunk line leads, switches at said first station for connecting the suhscriloers line to said trunk, switches at the distant station for extending said trunk, means for transmitting impulses from the subscribers line directly to the distant station over two conductors of said trunk line to control the operation of the switches therein, a source of talking current at said first station associated with said trunk line, a circuit including the third conductor of said trunk line, means for changing the condition of said circuit for a delinite interval of time, and means responsive to such change for rendering said source of current effective for conversation.

8. In a telephone system, a subscribers line, a satellite, a three-conductor trunk line outgoing therefrom, a distant exchange in which said trunk terminates, switches at the satellite for connecting the subscrihers line to said trunk, switches at the exchange for extending said trunk, a register controlling mechanism arranged to he set in accordance with numerical designations to control the operation of the switches in said exchange, means for transmitting impulses from the subscribers line over two conductors of said trunk line to the exchange to set said register controlling mechanism, a` source of talking current in the satellite associated with said trunk line, a circuit including the third conductor of said trunk line, means operated by said register controlling mechanisin upon the completion of its controlling operation for opening said circuit for a deiinite interval of time, and means responsive to such opening for rendering said source of current effective for conversation.

9. In a telephone system, asubscribers I* line, an automatic switch, a three-conductor connecting circuit, means for operating said switch to connect the subscribers line to said connecting circuit, asecond automatic switch in which said connecting circuit terminates, a controlling mechanism arranged to he set in accordance with numerical designations for controlling the operation ol said second automatic switch, means for transmitting impulses from the subscribers line over two conductors of said connecting circuit to set said controlling mechanism, a source of talking current at said iirst automatic switch associated with the connecting circuit, a controlling circuit including the third conductor of said connecting circuit, means operated by said controlling mechanism upon the completion ot its operation for changing the condition of said controlling circuit for a deiinite interval of time, means responsive to such change for rendering said source of current ei'lective for conversation, and means operated when the condition of said controlling circuit is changed for a longer interval of time to release said first automatic switch.

l0. In a telephone system, a subscribers line, a satellite, a three-conductor trunk line outgoing therefrom, a distant exchange in which said trunk line terminates, automatic switches in said satellite tor connecting the subscriber@ line to the trunk line, automatic switches in the exchange :tor extending said trunk line, registers for controlling the `operation of said automatic switches in the exchange, means for transmitting impulses from the subscribers line to the ei:- change over two conductors of said trunk line to set said registers, a source of talking current in the satellite associated with said trunk line, a controlling circuit including the third conductor of'said trunk line, means operated upon the completion of the operation of said registers for opening said controlling circuit for a definite interval oit time, means responsive to such opening for rendering said source of current effective for conversation,\and means responsive to the opening of said controlling circuit for a longer interval of time 'for releasing the automatic switches in said satellite.

11. In a telephone system, a subscribers line, a trunk line, an automatic switch for connecting the subscribers line to one end of said trunk, a second automatic switch at the other end of said trunk, an impulse circuit including the talking conductors of said trunk which is free from impedances, bridges, ground and other connections at said iirst switch for transmitting impulses from the subscribers line to operate said second switch, a source of talking current associated with the trunk line at said first switch, and means for rendering said source of current eiiective for conversation.

12. In a telephone system, a subscribers line, a trunk line, an automatic switch for connecting the subscribers line to one end of said trunk, a second automatic switch at the other end of said trunk, an impulse circuit including the talking conductors of said trunk which is free from impedances, bridges, ground and other connections at said first switch for transmitting impulses from the subscribers line to operate said second switch, a source of talking current associated with the trunk line at said first switch, and means controlled over said trunk line for rendering said source of current effective for conversation.

13. 1n a telephone system, a subscribers line, a trunk line, an automatic switch for connecting the subscribers line to one end or said trunk, a second automatic switch at the other end of said trunk, an impulse circuit including the talking conductors of said trunk which is 'free from impedances, bridges, ground and other connections at said irst switch ttor transmitting impulses from the subscribers line to operate said second switch, a source oi talking current associated with the trunk line at said .tirst switch, means for changing the condition of said trunk line for a predetermined interval of time, and means responsive to said change for rendering said source of current effective for conversation.

14k. ln a telephone system, a subscribers line, a trunk line, an automatic switch for connecting the subscribers line to one end ,of said trunk, a second automatic switch at the other end of said trunk, means for sending impulses from the subscribers line over said trunk, means responsive to such impulses i'or controlling said second switch to extend the. trunk line, a source of talking current at said first switch, means for changing temporarily the condition of said trunk line, and means responsive to said change of condition for rendering said source of current effective for conversation.

15.111 a telephone system, a subscribers line, a trunk line, an automatic switch for connecting the subscribers line to one end of said trunk line, a second automatic switch at the other end of said trunk, means for sending impulses from the subscribers line over said trunk, means responsive to such impulses for controlling said second switch to extend the trunk line, a source ci talking current at said first switch, a timing device requiring a predetermined interval oit time for completing its operation, and means controlled by said device for rendering said source of current effective for conversation. In witness whereof, I hereunto subscribe my name this 15th day of May A. D., 1919.

LUPA POLINKOWSKY. 

